A Perth man who masked the fatal shooting of his de facto wife as a suicide has been found guilty of her murder.

Robert Jeffrey Anderson shot Phaea Leanne Lightfoot, 51, in the bedroom of their Wanneroo home, north of Perth, during an argument about sex on August 29, 2012.

The West Australian Supreme Court heard that the couple, who met at a swingers club before striking up their relationship nine years ago, often argued about Anderson's inability to perform sexually for Ms Lightfoot, the ABC reports.

Robert Jeffrey Anderson has been found guilty of murdering his partner Phaea Leanne Lightfoot at the West Australian Supreme Court (pictured)

After Ms Lightfoot had died, Anderson placed the gun beside her body and told the triple-zero operator and police that she had killed herself, recordings played to the court revealed.

However when his trial began, Anderson admitted to shooting Ms Lightfoot, but claimed he had only intended to fire a warning shot through the bedroom door after she threw a ceramic cat at him.

He also denied intentionally placing the gun beside the body to make it appear like a suicide and rehearsing his story before calling for an ambulance.

Justice Michael Corboy said there had been a clear intent to at least cause injury, if not to kill.

'There was a deliberate shot fired at Ms Lightfoot and Mr Anderson was aiming to hit her as he fired,' he said.

Prosecutor Nick Cogin described the victim as a 'highly sexualised female' with an anger problem.

'She had a drug habit and was known to consume cannabis regularly. In addition she consumed methylamphetamine,' Mr Cogin said, according to the ABC.

He told the jury that her relationship with Anderson was a 'servant, slave relationship' in which she did as she was bid.

Anderson will appear in court again for sentencing submissions on January 23.